1. Technical Field
This disclosure relates to actuating systems, and, more particularly, to an apparatus and method for actuating a remotely locatable hydraulic mechanism with pressurized fluid.
2. Related Art
Valve actuating systems of the related art are typically hydraulically controlled mechanisms (HCMs) requiring the running of hydraulic control lines from a hydraulic fluid source to a valve actuator. The hydraulic fluid source is generally a supply tank of sufficient volume to accommodate the amount of hydraulic fluid required for the HCM with some amount of fluid in reserve. The hydraulic fluid is typically supplied to the valve actuating system through an arrangement of two control lines, which, depending upon the location of the valve actuator relative to the hydraulic fluid source, may necessitate a configuration of equipment that may be complex and expensive, especially in oilfield applications where the valve to be actuated is located downhole in a wellbore.
The hydraulic fluid supply tank is typically sized to accommodate two or three times the amount of hydraulic fluid required for normal operation of the HCM and is generally located at a well head of the wellbore. Because the volume of the supply tank is a function of the amount of the hydraulic fluid required for use in the system, an HCM remotely positioned relative to the well head could require a surface-located supply tank of a very large volume. In particular, a valve located downhole in a wellbore may be positioned at a depth such that miles of control line are required to actuate the valve. As the length of the control line is increased, the volume of hydraulic fluid required to maintain hydraulic pressure within the system correspondingly increases.
The control lines themselves occupy space within either the casing or the tubing string such that their presence detracts from the usable volume of the downhole environment. Because the control lines are conduits for fluids, they are typically of considerable size relative to electrical wiring or fiber optic cable. Furthermore, two control lines are typically required for each HCM. In an effort to minimize the number of control lines in the wellbore, one control line is usually run to each HCM and a common control line is shared by all of the HCMs. Nevertheless, operation of an oil well with multiple HCMs provides a challenge to surface-located operators because of the multiple connections involved and the possibility that control lines may cross each other within the wellbore and provide a source for fluid communication problems between the hydraulic fluid supply tank and the downhole environment.